The formation of reversal dye images in photographic elements is generally old and well known in the photographic arts. In a typical approach a photographic element capable of forming a multicolor image is imagewise exposed and developed in a black-and-white photographic developer composition. The undeveloped silver halide is next rendered developable by uniform exposure or by nucleation. The remaining silver halide is then developed using a color developing agent so that a positive dye image is formed. Reversal processing has proven quite attractive, since it offers a convenient approach for obtaining a positive dye image using a negative-working silver halide emulsion without the necessity of first producing a negative dye image and then reexposing a second photographic element through the negative dye image. Reversal processing to form positive dye images is widely employed in producing color photographic transparencies.
In my U.S. Pat. No. 3,862,842, issued Jan. 28, 1975, I disclose a process of forming a reversal dye image using a redox amplification process in which a cobalt(III) complex is employed as an oxidizing agent. Example 10 illustrates that in attempting to undertake reversal processing using a cobalt(III) complex as an oxidizing agent both the black-and-white and the color developed silver acts as a redox amplification catalyst. Unless a step is interposed in the process to remove the black-and-white developed silver, no reversal dye image can be obtained. Specifically, in Example 10 a control strip (1) is given a conventional reversal processing. A strip (2) is identically processed, except that 1.6 grams/liter of cobalt hexammine chloride are added to the color developer solution. The result is that instead of forming a dye image a uniform high density of dye is formed in each of the red, green and blue sensitive layers of the photographic element being processed--that is, maximum and minimum density measurements were identical. A third strip (3) was processed identically as strip (2), but with the variation that after a silver image had been formed through initial exposure and black-and-white development, the silver image was removed by bleaching. In strip (3) a reversal dye image was obtained having an enhanced maximum dye density in each of the red, green and blue sensitive layers.
In my U.S. Pat. No. 3,862,842 I refer to column 9, lines 35 through 39, to the photolytic formation of a development inhibitor, such as phenylmercaptotetrazole. In my pending U.S. patent application Ser. No. 420,193, filed Nov. 28, 1973, this same statement appears with the intended teaching being illustrated by the examles. In Example 1 a photographic element is formed containing palladium nuclei and a color coupler in a first layer coated on a photographic support. This layer is overcoated with an oxidized color developing agent scavenging layer which is in turn overcoated with a negative-working silver bromoiodide emulsion layer containing a development inhibitor releasing (DIR) coupler capable of liberating phenylmercaptotetrazole upon silver development. The photographic element is used to form a positive dye transfer image by imagewise exposing the emulsion layer and then processing by bringing a receiver bearing a mordant and soaked with a color developer composition containing cobalt hexammine chloride and a silver solvent into contact with the exposed emulsion layer. As development occurs in the emulsion layer, phenylmercaptotetrazole is released from the DIR coupler and migrates to the first layer containing the palladium nuclei. This results in catalyst poisoning so that a redox amplification occurs in the first layer involving the cobalt hexammine as an oxidant and the color developing agent as a reducing agent only in the unexposed areas of the element. The oxidized color developing agent formed by the redox reaction in turn reacts with the color coupler contained in the first layer to form a mobile dye which diffuses to the receiver and forms a positive dye image in the receiver.
It is known in the art that in the presence of a catalyst a peroxide oxidizing agent can enter into a redox amplification reaction with a color developing agent to produce a dye image in a photographic element. The formation of positive dye images using peroxide oxidizing agents is generally known in the art. In Matejec et al U.S. Pat. No. 3,694,207, issued Sept. 26, 1972, positive dye images are formed by providing a uniform coating of a peroxide redox catalyst on a photographic support. Upon imagewise exposure the redox catalyst is destroyed in light-struck areas. Using a peroxy redox amplification reaction a positive dye image is formed in the areas where the catalyst remains. In Matejec et al U.S. Pat. No. 3,776,730, issued Dec. 4, 1973, a positive dye image is formed in a peroxide redox amplification process by imagewise exposing a silver halide photographic element containing a negative-working emulsion. The emulsion is developed using a black-and-white developer to form a negative silver image. Upon treatment with peroxide, the peroxide is quickly decomposed in the areas containing the silver image, thereby leaving behind a peroxide distribution corresponding to the unexposed areas of the photographic element. By incorporating in the photographic element substances which will decompose the peroxide at a slower rate than the silver image, the residual peroxide in the unexposed areas can be slowly decomposed under conditions which promote the formation of a positive image. Either a dye or a vesicular positive image can be formed.
It is known in the art that heterogeneous catalyst surfaces for peroxide redox amplification reactions can be poisoned by adsorbed materials. This is pointed out in Research Disclosure, Vol. 116, Item No. 11660, titled "Image Amplification Systems," published December, 1973. A number of materials are disclosed which tend to become adsorbed to the surface of catalytic noble metal nuclei and thereby to interfere with peroxide oxidizing agent redox reactions with color-developing agents. These include adsorbed stabilizers, antifoggants and spectral sensitizing dyes. Azoles and thiazoles which are free from mercaptan and ionic iodide moieties are taught to be useful without fouling catalytic surfaces. Mercaptotetrazoles, -oxazoles, and -imidazoles are taught to be avoided. Since peroxide-containing amplifier solutions may be poisoned by bromide ions or antifoggants carried over from conventional development solutions, it is taught to limit developing solution potassium bromide or antifoggant concentrations to no greater than 1 gram per liter. In Example 5 it is shown that when 2 grams of potassium bromide was incorporated in a liter of the color developer composition, no amplification was obtained using a peroxide oxidizing agent; when the developer contained 200 mg per liter of 5-methyl benzotriazole both antifoggant and amplification effects were satisfactory; when the developer contained 200 mg per liter of 3-methyl-1,3-benzothiazolium iodide, no amplification was obtained; and when the developer contained 200 mg per liter of decamethylene bisbenzothiazolium bromide, both antifoggant and amplification effects were satisfactory. This is corroborated by Matejec U.S. Pat. No. 3,674,490, issued July 4, 1972, which refers to a silver catalyst surface for a peroxide redox amplification reaction being "purified" by displacement of adsorbed, inactivating substances (e.g., emulsion stabilizers), to increase its catalytic activity.